Constant Potential Coulometric Measurements with Ca²⁺-Selective Electrode: Analysis Using Calibration Plot vs. Analysis Using the Charge Curve Fitting

Abstract

The possibility of analysis using charge curve fitting in constant potential coulometric mode instead of using a calibration plot is explored, for the first time. The results are compared with the analysis based on the use of a calibration plot. A Ca2+ ion-selective electrode, with and without an electronic capacitor in series, is used as a model system in pure solutions of CaCl2. Both techniques delivered good results (error within 2%) when the final and the initial concentration values differed by not more than three times. Larger differences result in 10–25% error. The presence of an electronic capacitor in the measurement circuit and in series with the electrode, allows for significantly faster response.

Keywords

• calcium ion activity
• constant potential coulometry
• analysis
• calibration plot
• charge curve fitting